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United States Patent |
5,530,296
|
Masaki
|
June 25, 1996
|
Power supply switching apparatus
Abstract
A power supply switching apparatus for switching power supplies used to all
electronic appliance such as a pager and a portable telephone is
described. A battery pack includes a battery and is connectable to an
external DC power supply. In the battery pack, a power supply connection
detecting circuit detects whether or not the external DC power supply is
connected to this battery pack, and a switching circuit switches the
battery and the external DC power supply. In an appliance housing a
voltage is detected by a voltage detecting circuit to judge whether the
detected voltage corresponds to the voltage derived from the battery power
supply, or the voltage derived from the external DC power supply, and
another switching circuit switches the battery power supply and a power
stabilizing circuit. Both of these battery pack and appliance housing
constitute the power supply switching apparatus.
Inventors:
|
Masaki; Tateo (Ichikawa, JP)
|
Assignee:
|
Uniden Corporation (JP)
|
Appl. No.:
|
176397 |
Filed:
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December 30, 1993 |
Foreign Application Priority Data
Current U.S. Class: |
307/75; 307/64; 307/150; 320/DIG.10 |
Intern'l Class: |
H02J 007/00 |
Field of Search: |
307/64,66,75,150,80,85
320/2
|
References Cited
U.S. Patent Documents
4590943 | May., 1986 | Paull et al. | 307/150.
|
4675538 | Jun., 1987 | Epstein | 307/64.
|
4709201 | Nov., 1987 | Schaefer et al. | 320/2.
|
5019767 | May., 1991 | Shirai et al. | 320/2.
|
5191229 | Mar., 1993 | Davis et al. | 307/66.
|
5287053 | Feb., 1994 | Hutchinson | 307/66.
|
5347163 | Sep., 1994 | Yoshimura | 307/66.
|
5381043 | Jan., 1995 | Kohiyama et al. | 307/150.
|
5404090 | Apr., 1995 | Shinbori | 320/2.
|
Foreign Patent Documents |
50-86642 | Jul., 1975 | JP.
| |
Primary Examiner: Shoop, Jr.; William M.
Assistant Examiner: Kaplan; Jonathan
Attorney, Agent or Firm: Ratner & Prestia
Claims
The Invention claimed is:
1. A power supply switching apparatus for a portable appliance for
switching between a battery power supply and an external DC power supply,
the battery power supply being housed in a battery pack, the battery pack
providing a voltage to the portable appliance to which the battery pack is
removably mounted, the apparatus comprising:
first apparatus located in said battery pack including:
means for connecting said battery pack to said external DC power supply;
means for selecting one of said battery power supply and said external DC
power supply; and
means for applying a voltage of said selected power supply to said portable
appliance, and
second apparatus located in said portable appliance including;
means for receiving the voltage applied from said battery pack;
means for detecting whether the received voltage corresponds to the voltage
applied from said battery power supply, or the voltage applied from said
external DC power supply;
a power stabilizing circuit for stabilizing the voltage from the external
DC power supply to output a stabilized voltage; and
means for switching between the voltage from said means for receiving and
the stabilized voltage from said power stabilizing circuit to output the
switched voltage in response to an instruction from said detecting means.
2. A power supply switching apparatus for a portable appliance for
switching between a battery power supply and an external DC power supply ,
the battery power supply being housed in a battery pack, the battery pack
providing a voltage to the portable appliance to which the battery pack is
removably mounted, the apparatus comprising:
first apparatus located in said battery pack including:
means for connecting said battery pack to said external DC power supply,
power supply connection detecting means for detecting whether or not said
external DC power supply is connected to said battery pack;
first switching means for switching between said battery pack supply and
said external DC power supply in response to an instruction issued from
said power supply connection detecting means; and
means for applying the voltage of said switched power supply to said
portable appliance; and,
second apparatus located in said portable appliance including;
means for receiving the voltage applied from said battery pack;
means for detecting whether the received voltage corresponds to the voltage
applied from said battery power supply, or the voltage applied from said
external DC power supply;
a power stabilizing circuit for stabilizing the voltage from the external
DC power supply to output a stabilized voltage; and
means for switching between the voltage from said means for receiving and
the stabilized voltage from said power stabilizing circuit to output the
switched voltage in response to an instruction from said means for
detecting means.
3. A power supply switching apparatus for a portable appliance for
switching between a battery power supply and an external DC power supply,
the battery power supply being housed in a battery pack, the battery pack
providing a voltage to the portable appliance to which the battery pack is
removably mounted, said apparatus comprising:
first apparatus located in said battery pack including:
means for connecting said battery pack to said external DC power supply;
a power supply connection detecting circuit for detecting a connection of
said external DC power supply to said battery pack;
a first switching circuit for switching between said battery power supply
and said external DC power supply in response to an instruction issued
from said power supply connection detecting circuit to output one of said
voltages derived from said battery power supply and said external DC power
supply; and
a first connection terminal for supplying the voltage output from said
switching circuit to said portable appliance; and,
second apparatus located in said portable appliance including;
a second connection terminal connected to said first connection terminal;
a voltage detecting circuit for detecting whether a voltage applied from
said battery pack to said second terminal corresponds to the voltage
derived from said battery power supply, or the voltage derived from said
external DC power supply;
a power stabilizing circuit for stabilizing the voltage applied to said
second connection terminal to output a constant voltage; and
a second switching circuit for switching between said second connection
terminal and said power stabilizing circuit in response to an instruction
issued from said voltage detecting circuit, and for applying the constant
voltage derived from one of said second connection terminal and said power
stabilizing circuit to a predetermined power source circuit of said
portable appliance.
4. A power supply switching apparatus as claimed in claim 3, wherein:
said external DC power supply connection detecting circuit and said first
switching circuit are constructed of a jack with a switch, wherein the
jack receives a power supply plug by which said external DC power supply
is connected to said battery pack; and
when said power supply plug is inserted into said jack, said switch is
opened, thereby connecting said external DC power supply to said first
connection terminal, and when said power supply plug is not connected to
said jack, said switch is closed, thereby connecting said battery to said
first connection terminal.
5. A power supply switching apparatus for a portable appliance for
switching between a battery power supply and an external DC power supply,
the battery power supply being housed in a battery pack, the battery pack
providing a voltage to the portable appliance to which the battery pack is
removably mounted, wherein:
said battery pack comprises:
a jack with a switch, said jack receiving a power supply plug for
connecting said external DC power supply to said battery pack, said jack
having a plus-sided contact and a minus-sided contact, said switch
connecting the minus-sided contact to a minus polarity of said power
supply, said switch being opened when said power supply plug is inserted
into said jack, and said switch being closed when said power supply plug
is not connected to said jack;
a first plus-sided connection terminal connected to said plus-sided contact
of said jack and a positive polarity of said battery power supply; and
a first minus-sided connection terminal connected to said minus-sided
contact of said jack and a positive polarity of said battery power supply;
and
said portable appliance comprises:
a second plus-sided connection terminal connected to said first plus-sided
connection terminal;
a second minus-sided connection terminal connected to said first
minus-sided connection terminal;
a voltage detecting circuit including a series circuit constructed of a
zener diode and a resistor, said series circuit connecting said second
plus-sided connection terminal to said second minus-sided connection
terminal, for detecting whether a voltage applied from said battery pack
to said second plus-sided connection terminal and said second minus-sided
connection terminal, corresponds to the voltage derived from said battery
power supply, or the voltage derived from said external DC power supply;
a power stabilizing circuit connected to said second plus-sided connection
terminal and said second minus-sided connection terminal, for stabilizing
the voltage applied from said battery pack via said plus-sided connection
terminal and said second minus-sided connection terminal; and
a switching circuit for switching between the voltage on said second
plus-sided connection terminal and said second minus-sided connection
terminal, and the output voltage from said power stabilizing circuit,
thereby outputting one of said switched voltages.
6. A power supply switching apparatus as claimed in claim 5, wherein a
recharging resistor connects the negative polarity of said battery and
said minus-sided contact.
7. A power supply switching apparatus as claimed in claim 5, wherein a
zener voltage of said zener diode is selected to be an intermediate
voltage between the voltage of said battery power supply and the voltage
of said external DC power supply.
8. A power supply switching apparatus for a portable appliance for
switching between a battery power supply and an external DC power supply,
the battery power supply being housed in a battery pack, battery pack
providing a voltage to the portable appliance to which the battery pack is
removably mounted, the apparatus comprising:
first apparatus located in said battery pack including:
means for connecting said battery pack to said external DC power supply;
an external DC power supply connection detecting circuit for detecting
whether the external DC power supply is connected to said battery pack;
a recharging circuit for recharging said battery power supply housed in
said battery pack when said external DC power supply is connected to said
battery pack;
a switching circuit, responsive to said external DC power supply connection
detecting circuit, for switching between said external DC power supply and
said battery supply and for providing one of said external DC power supply
and said battery supply to said portable appliance; and
second apparatus located in said portable appliance including:
a voltage detecting circuit for receiving a voltage from said battery pack
and detecting whether the source of the voltage is said external DC power
supply or said battery supply;
a power stabilizing circuit for stabilizing the voltage from said external
DC power supply and providing a stabilized voltage; and
a switching circuit, responsive to said voltage detecting circuit, for
switching between said voltage from said battery pack and said stabilized
voltage and providing one of said voltage from said battery pack and said
stabilized voltage to circuitry within said portable appliance.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention generally relates to a power supply switching
apparatus. More specifically, the present invention is directed to a
circuit for switching power supplies to compact pagers, portable
telephones and so on.
2. Description of the Prior Art
In recently developed/marketed portable appliances such as pagers and
portable telephones, battery packs mounted to housings of these appliances
are made compact in connection with the compact of the portable
appliances. Conventionally, a rechargeable cell (battery), a power
stabilizing circuit, and a switching circuit for switching the
rechargeable cell into the power stabilizing circuit when a portable
appliance is connected to an external DC power supply, are provided within
a battery pack.
However, as described above, the more, the battery pack is made compact,
the narrower the space capable of storing the switching circuit and the
power stabilizing circuit are available. There is another problem that
since heat dissipation of the power stabilizing circuit becomes large,
this power stabilizing circuit may not be readily stored in such a compact
battery pack. Furthermore, there is another drawback that when the
switching circuit and the power stabilizing circuit would be stored within
the battery pack, the number of connection terminals for connecting the
battery pack with the appliance housing should become large.
SUMMARY OF THE INVENTION
An object of the present invention is to be acceptable for a demand to make
a compact battery pack, and is to provide a power supply switching
apparatus capable of reducing a total number of connection terminals for
connecting a housing of an electronic appliance with a battery pack.
To achieve the above-described object, according to one aspect of the
present invention, a power supply switching apparatus comprises a battery
power supply, for switching between said battery power supply and an
external DC power supply when a voltage from a battery pack connectable to
said external DC power supply is applied to a portable appliance to which
the battery pack is detachably mounted,
the above-described battery pack includes:
means for selecting said battery power supply and said external DC power
supply; and
means for applying a voltage of said selected power supply to said portable
appliance,
the above-described portable appliance includes:
means for receiving the voltage applied from said battery pack;
means for detecting whether the received voltage corresponds to the voltage
applied from said battery power supply, or the voltage applied from said
external DC power supply;
a power stabilizing circuit for stabilizing the voltage from the external
DC power supply to output a stabilized voltage; and
means for switching between the voltage from said battery power supply and
the stabilized voltage from said power stabilizing circuit to output the
switched voltage in response to an instruction from said detecting means.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a schematic block diagram arrangement of a power supply switching
apparatus according to an embodiment of the present invention; and
FIG. 2 is a concrete circuit diagram of the power supply switching
apparatus shown in FIG. 1.
DESCRIPTION OF THE EXEMPLARY EMBODIMENTS
FIG. 1 is a schematic block diagram of a basic circuit arrangement of a
power supply switching apparatus according to an exemplary embodiment of
the present invention. The power supply switching apparatus is arranged by
an external DC power supply connection detecting circuit 12 stored within
a battery pack 10, a recharging circuit 14, a rechargeable battery (cell)
16 such as an Nickel-cadmium battery cell, a switching circuit 18, a
voltage detecting circuit 22 stored within an appliance housing 20, a
power stabilizing circuit 24, and another switching circuit 26.
The battery pack 10 is equipped with a power supply jack 11 connectable to
an external DC power supply (not shown). This battery pack 10 is further
comprised of a power supply connection terminal 19 which is connected with
another power supply connection terminal 21 of the appliance housing 20
when the battery pack 10 is mounted to this appliance housing 20. The
power supply connection detecting circuit 12 employed within the battery
pack 10 is such a circuit for detecting an electric connection established
between the power supply jack 11 and the external DC power supply.
Conceretely speaking, when a power supply plug is inserted into the power
supply jack 11, this insertion is detected by the power supply connection
detecting circuit 12. The switching circuit 18 switches power supplied
from the rechargeable battery 16 into power supplied from the external DC
power supply when the connection of the external DC power supply is
detected by the power supply connection detecting circuit 12.
The voltage detecting circuit 22 employed in the appliance housing 20 is a
circuit for detecting the voltage of the power supply in order to judge
whether the voltage applied via the power supply connection terminal 21
from the battery pack 10 corresponds to the voltage from the battery power
source, or the voltage from the external DC power supply. The power
stabilizing circuit 24 is such a circuit for stabilizing the input voltage
derived from the external DC power supply connected to the battery pack 10
thereby maintaining the constant output voltage even when the power source
voltage and/or the load are varied. The switching circuit 26 switches the
voltages derived from the the battery 16 and the power stabilizing circuit
24 in response to an instruction supplied from the voltage detecting
circuit 22, thereby outputting the switched voltage. With the above
described circuit arrangement, when the battery pack 10 is mounted to the
appliance housing 20 and the external DC power supply is not connected
thereto the switching circuit 18 of the battery pack 10 switches to
connect the rechargeable battery 16 in response to the instruction issued
from the power supply connection detecting circuit 12, so that the voltage
of this battery 16 is applied via the switching circuit 18 and the power
supply connection terminal 19 to the power supply connection terminal 21
of the appliance housing 20. On the other hand, when the external DC power
supply is connected to the battery pack 10, the switching circuit 18
switches the battery 16 into the external DC power supply in response to
another instruction derived from the power supply connection detecting
circuit 12, whereby the voltage of the external DC power supply is
supplied via this switching circuit 18 and the power supply connection
terminal 19 to the power supply connection terminal 21 of the appliance
housing 20. The voltage detecting circuit 22 of the appliance housing 20
detects the voltage of the power supply connection terminal 21 to judge
whether the detected voltage corresponds to the voltage derived from the
external DC power supply, or the voltage derived from the battery 16, so
that the switching circuit 26 may be controlled based upon the judgement
result. Under control of the voltage detecting circuit 22 the switching
circuit 26 switches to the power stabilizing circuit 24 when the voltage
derived from the external DC power supply is received, and switches to the
power supply connection terminal 21 when the voltage derived from the
battery 16 is received. The switching circuit 26 applies either the
voltage from the battery 16, or the voltage from the power stabilizing
circuit 24 to a predetermined circuit within the appliance housing 20.
FIG. 2 represents one example of a concrete circuit arrangement of the
power supply switching apparatus shown in FIG. 1.
The battery pack 10 is equipped with a jack 32 having a switch whose
plus-sided contact 34 is connected to an anode of a reverse connection
preventing diode 36. A cathode of this diode 36 is connected to a plus
sided connection terminal 38a. A minus-sided contact 35 of this jack 32 is
connected to a minus-sided connection terminal 38b. A cathode of the diode
36 is connected to a plus-sided terminal of the Nickel-cadmium battery 40.
A minus-sided terminal of the battery 40 is connected to one end of a
recharging resistor 42. The other end of this recharging resistor 42 is
connected to the minus-sided contact of the jack 32. A switch 44 of the
jack 32 is connected parallel to the recharging resistor 42. This switch
44 owns such a construction that when the external DC power source plug
(not shown in detail) is inserted into the jack 32, this switch 44 is
opened, whereas when this plug is pulled out from the jack 32, this switch
44 is closed.
With respect to the above-described construction of the battery pack 10,
the jack with switch 32 corresponds to the power supply connection
detecting circuit 12 and the switching circuit 18, the recharging resistor
42 corresponds to the recharging circuit 14 of FIG. 1, and the connection
terminals 38a and 38b correspond to the power supply connection terminal
19 of FIG. 1.
On the other hand, the appliance housing 20 comprises a zener diode 50
whose cathode is connected to a plus-sided connection terminal 52a. An
anode of this zener diode 50 is grounded via a resistor 54. A junction 60
between this anode and the resistor 54 is connected via a resistor 58 to a
base of an NPN transistor 56. An emitter of this NPN transistor 56 is
grounded, and a collector thereof is connected to a base of another NPN
transistor 68, and also via a resistor 47 to the plus-sided connection
terminal 52b of this appliance body 20.
An emitter of the transistor 68 is grounded, and a collector thereof is
connected via a resistor 70 to a base of a PNP transistor 66. An emitter
of this transistor 66 is connected to the plus-sided connection terminal
52a, and a collector thereof is connected to a voltage supply terminal 76.
A resistor 72 is connected between the base of the transistor 66 and the
emitter thereof.
The appliance housing 20 further includes an NPN transistor 62 whose
collector is connected to the plus-sided connection terminal 52a and whose
emitter is connected to the voltage supply terminal 76. A base of this
transistor 62 is connected to a cathode of another zener diode 64, the
emitter of which is grounded. A resistor 65 is connected between the base
of the transistor 62 and the collector thereof.
With respect to the above-described circuit arrangement of the appliance
housing 20, the circuit arrangement constructed of the zener diode 50,
transistor 56, and resistors 54, 58 corresponds to the voltage detecting
circuit 22 of FIG. 1. Another circuit arrangement constructed of the
transistor 62, zener diode 64, and resistor 65 corresponds to the power
stabilizing circuit 24, a circuit arrangement arranged by the transistor
66, transistor 68, and resistors 70, 72 corresponds to the switching
circuit of FIG. 1, and the connection terminals 52a and 52b correspond to
the power supply connection terminal 21 of FIG. 1.
In the power supply switching apparatus shown in FIG. 1, it is selected
that the external DC power supply is DC 12 V, the Nickel-cadmium battery
40 is DC 6 V, and the output voltage of the power stabilizing circuit is
DC 6 V. At this time, a zener voltage of the zener diode 50 of the voltage
detecting circuit is selected to be DC 8 V.
Operations of the power supply switching apparatus shown in FIG. 2 will now
be explained. When the rechargeable battery 40 of the battery pack 10 is
recharged, the battery back 10 is released, or dismounted from the
appliance housing 20, and then the external DC power source plug is
inserted into the jack 32. When this power source plug is inserted into
the jack 32, the switch contact 44 of this jack 32 is opened to form a
loop circuit of the plus-sided contact 34, diode 36, battery 40,
recharging resistor 42, and minus-sided contact 35, so that the battery 40
is brought into the recharging condition.
Subsequently, power supply switching operations under such condition that
the battery pack 10 is mounted to the appliance housing 20 will now be
described. When the battery pack 10 is mounted on the appliance housing
20, the connection terminals 38a, 38b are connected to the connection
terminals 52a, 52b. When the external DC power supply plug has not yet
been inserted into the jack 32, the switch 44 is closed and the battery 40
is connected to the connection terminals 38a and 38b. Accordingly, a DC
voltage of 6 V is applied between the connection terminals 52a and 52b of
the appliance body 20.
Since the voltage applied from the battery 40 is lower than the zener
voltage of 8 V, the zener diode 50 of the voltage detecting circuit in the
appliance housing 20 is under OFF state. Therefore, the transistor 56 is
turned OFF, so that the transistor 68 of the switching circuit 26 is
turned ON and the transistor 66 is turned ON. As a result, the voltage of
the battery 40 is output from the voltage supply terminal 76.
When the external DC power source plug is inserted into the jack 32, the
switch 44 is opened and then the voltage is applied across the connection
terminals 38a and 38b, namely the connection terminals 52a and 52b of the
appliance housing 20. As previously stated since the voltage of the
external DC power supply is selected to be DC 12 V the zener diode 50 of
the voltage detecting circuit is turned ON and the transistor 56 is also
turned ON. As a result, the transistor 68 of the switching circuit is
turned OFF and the transistor 66 is turned OFF.
On the other hand, the DC voltage of 12 V derived from the external DC
power supply is applied via the connection terminals 52a and 52b to the
zener diode 64 and the resistor 65 of the power stabilizing circuit. Due
to the constant voltage characteristic of the zener diode 64, the
stabilized DC 6 V may be applied to the voltage supply terminal 76. Then,
the DC voltage output from the voltage supply terminal 76, is supplied to
a predetermined circuit arrangement of the appliance housing 20.
In accordance with the embodiment of the present invention, since only the
battery, recharging resistor and diode are employed in the battery pack, a
demand for compactness can be satisfied. A total number of power supply
connection terminals used to connect the appliance housing with the
battery pack is only 2, so that the quantity of the power supply
connection terminals can be considerably reduced, as compared with that of
the conventional power supply switching apparatus which contains the power
stabilizing circuit and the switching circuit within battery pack.
While the present invention has been described using a specific embodiment,
it should be understood that further modifications and changes can be made
without departing from the scope of the present invention.
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